Process for the production of beta-carboxy-ethyl-substituted or ganopolysiloxanes



United States Patent "ice 9 Claims. (c1.260-44s.2

The present invention relates to an effective and versatile process for the production of organopolysiloxanes of the general empirical formula wherein n is a whole or fractional number which is greater than one and at most equal to 3 and wherein at least one of the individual substituents R of the polysiloxane is a fi-carboxyethyl radical linked to silicon and each of the other substituents R is a hydrocarbon radical, at least half of said other substituents R being methyl, the remaining thereof, if any, being phenyl or vinyl. Preferably the hydrocarbon radicals in these siloxanes are all methyl, or methyl and phenyl, or methyl and vinyl.

1,3 di (fi-carboxyethyl)-tetramethyl-disiloxane of the formula represents one of the simplest examples of these organopolysiloxanes, and several methods are known for its production. In this regard, it is possible to hydrolyze and condense fi-carboxyethyl-trimethyl-silane with sulfuric acid whereby methane is formed, but the procedure is uneconomic since a Si-C bond formed with much trouble (for instance by a Grignard reaction) is decomposed again. It is also possible to prepare dimethyl-(;8,fi-dicarbethoxy-ethyl)-ethoxy-silane from dimethyl-(chloromethyD-ethoxy-silane by a malonic ester synthesis and then to hydrolyze this product with acid. It is again possible to prepare pentamethyl-(5,;3-dicarbethoxy-ethyl)-disiloxane from pentamethyl-(iodomethyl)-disiloxane by a malonic ester synthesis or to prepare pentamethyl-(flcarbethoxy-fl-cyanoethyl)-disiloxane from such iodomethyl-disiloxane by a cyanoacetic acid ester synthesis and then to submit these disiloxanes to hydrolysis with acid whereby disproportionation occurs. In such case, however, half of the siloxane units are converted to hexarnethyldisiloxane which is inevitably formed as the side product.

Whereas these previously known processes for the production of a carboxyethyl-substituted disiloxane are not really satisfactory for commercial manufacture, the methods of production of higher polysiloxanes therefrom are even less suitable. Since the method known as equilibration otherwise in common use for the copolymerization of a disiloxane with other siloxanes fails in this case, a lactone being formed by the elimination of water, the only method known up to the present consists of the possibility of first converting di-(carboxyethyl)-tetramethyl-disiloxane to B-(dimethyl-chlorosilyl)-propionyl chloride and then hydrolyzing this product when mixed with other organochlorosilanes, for instance dimethyldichlorosilane.

It is an object of the present invention to overcome the foregoing disadvantages and to provide a particularly effective and versatile process for this production of organopolysiloxanes.

It is another object of the present invention to provide 3,391,177 Patented July 2, 1968 organopolysiloxanes of the instant type by a single step overall process.

It is a still further object of the present invention to provide such a process for producing organopolysiloxanes utilizing a B-organosilyl-a-cyanopropionic acid ester in admixture with one or more organochlorosilanes or one or more organosiloxanes in a strongly acidic aqueous medium until hydrolysis and co-condensation take place.

It is a still further object of the present invention to provide a process of the foregoing type for the production of organopolysiloxanes wherein hydrolysis, decarboxylation and co-condensation reactions indigenous to the process all proceed side by side during the single procedural operation.

It is a still further object of the present invention to provide such a process which reduces the overall reaction time and avoids cumbersome multiple step manipulations for achieving the desired end product.

It is a still further object of the present invention to provide a process of the foregoing type for producing such organopolysiloxanes which may be utilized effectively as surfactants, and plastics modifiers, etc.

Other and further objects of the present invention will become apparent from a study of the within specification and accompanying examples.

It has now been found in accordance with the present invention that a particularly effective and versatile single step overall process for the production of B-carboxyethyl-substituted organopolysiloxanes, as defined above, may now be provided which comprises heating a B-organosilyl-a-cyanopropionic acid ester of the general formula wherein m is 1 or 2 and each of the substituents R is methyl or ethyl, in a strongly acidic aqueous medium in admixture with one or several organochlorosilanes of the general formula or one or several organosiloxanes of the empirical formula wherein a is a number being at most equal to 3 and being in any case chosen so that the average of all numbers a in the total sum of the organosilicon compounds present in the reaction mixture is greater than 1, and each substituent R" is a silicon bonded hydrocarbon radical selected from the group consisting of methyl, phenyl, and vinyl, the proportion of phenyl or vinyl being chosen so that at least half of all the said hydrocarbon radicals R contained in the reaction mixture are methyl, until hydrolysis and co-condensation take place.

When the organosiloxanes R".sio

are employed as starting materials in accordance with the present invention, such as for example hexamethyl-disiloxane, hexamethyl-cyclo-trisiloxane, octamethyl-cyclotetrasiloxane and a,w-bis-(trimethylsiloxy)-polydiorganosiloxanes, the hydrolysis operation is preferably carried out in a reaction medium consisting of a mixture of hydrochloric acid having 20 to 38 percent by weight HCl and concentrated acetic acid, the alkyl ester of acetic acid which is formed during this operation being continuously distilled off.

When the organochlorosilanes R,,SiCl are employed as starting materials in accordance with the present invention, for instance trimethyl-chlorosilane, dimethyl-di- 4 chlorosilane, methyl trichlorosilane, methyl pnenyl dii345 g. l3 mole) of 13-(dimethyl-methoxy-silyl)-a-cyano chlorosilane or methyl-vinyl-dichlorosilane. it is preterred propionic acid ethyl ester are mixed with 150 g. (1 mole) to employ acetic acid in a sufficient amount of water for tiif methyl-trichlorosilane, 1935 g. (15 mole) of dimethylhydrochloric acid having to 38 percent by weight HCl tiichlorosilane and 573 g. (3 mole) of methyl-phenyl-dito be formed when all Cl-Si bonds have been hydrolyzed. t5 chlorosilane and the mixture is added dropwise with stir- As the artisan will appreciate, various inorganic acids ring in the course of 2 hours to a solution of 1 litre of may be used together with various organic acids to proglacial acetic acid in 2.5 litres of water. Then the mixture vide the strongly acidic aqueous medium for the required is heated to boiling under a fractionating column, so that hydrolysis, decarboxylation and co-condensation reactions. the methyl acetate and the ethyl acetate formed during However, as being the simplest and cheapest or" those M) the reaction are continuously distilled off through such acids, hydrochloric acid and acetic acid are preferred. column. When no more ester distills, the residue is mixed Of especial advantage in accordance with the process with 2 litres of a saturated solution of sodium chloride; of the present invention, is the fact that the various stages the oil phase is separated and then washed again with 1 of reaction; i.e. the hydrolysis of the ester groups on the litre of sodium chloride solution. The resultant oil is carbon atom and on the silicon atom and of the nitrile 5 dried over sodium sulfate and then freed from volatile group, the decarboxylation, the hydrolysis of the chlorocomponents by heating to 80 C. at 1 mm. Hg. After silanes optionally employed at the same time, and the coliltration 1650 g. (approximately 82 percent of the theocondensation of the siloxanes; all proceed side by side l'etical amount) of a yellowish oil are obtained, having during a single operation. Accordingly, both prolonged ti refractive index of n :1.4248. Its viscosity amounts reaction times and cumbersome multiple step man1pula- 30 to 180 cst. at 20 C. and its acid number is 88. tions are specifically avoided.

The ,B-organosilyl-ot-cyanopropionic acid esters to be Examp 1e 3 employed for the process of the present invention have Example 2 is repeated in all analOgOus manner, 1 also become readily available by a novel process for their lively, utilizing instead of Inethyl-Pbyl-dichlofosilane production disclosed in our copending application Ser. 3 mole of methyl-vinyl-dichlorosilane, and p y y- No. 425,935, filed Jan. 15, 1965, when an alkyl ester of ails, decarboxylation, cocondensation and distillation, the

cyanoacetic acid is heated with an organo-bromomethyliiorl'esponding Organopolysiloxane is Obtainedsilane in the presence ofatertiary ami it will be appreciated, therefore, that the present in- The carbofunctional organosiloxanes Obtained aord t ention covers a versatile and effective single step overall ing to the instant invention can be employed effectively, I process for the Production of ersenepelysilexenes of the as the artisan will appreciate, as surfactants, for instance ti emplfical formula as emulsifiers, and for the modification of plastics, for

instance of polyesters, siloxane elastomers or organopoly- T slloxane in which a is a number having a value greater than 1 The following examples a e given for Purpose and atmost equal to 3, at least one individual R subillustrating, wh1le not limiting, the present invention. ymuent is gcarboxyethyl linked to silicon and each f Example 1 the remaining R substituents respectively is a hydrocar- 183 g. (0.8 mole) of B-dimethyl-ethoxy-srlyl)-a-cyanot5 bon radical selected from the group consisting of methyl,

propionic acid ethyl ester are mixed with 297 g. ti mole) phenyl, and vinyl, which comprises heating a fl-organoof octamethyl-cyclo-tetrasiloxane, 300 cc. of hydrochloric tilyl-u-cyanopropionic acid ester of the formula 301d (38 percent by weight of HCl) and 300cc. of glacial ,tCHO SKOR') CH, CH .C .O acetic acid and the mixture is heated to boiling under a fractionating column, so that the ethyl acetate formed ON 0 during the reaction is continuously distilled off through in which m is an integer having a value from 1 t and such column. When no more ester distills, the excess of hash of 1116 substitllents is an alkyl radical having 1 acid is for the most part evaporated ff d h id to 2 carbon atoms, in a strong acidic aqueous medium in is then washed twice with a solution of 10 percent by admixture with at least one organosilicon comopund seweight of sodium chloride in water. The resultant oil is .11.; tested from the group consisting of orgenechlerosilanes dried over sodium sulfate and then freed from volatile uf e formula "t t e and ersanesilexanes o the components by heating to C. at 1 mm. Hg. The prod- Empirical formula uct has a refractive index of n =L4186 and its viscosity R" si 4 amounts to 108 cst. at 20 C., its acid number being 112. Its absorption at 5.85 t in the infrared spectrum is due to no 2 the carboxyl group, but it has no absorption correspond i Whlch 1S a number havmg a value of at ,most 3 yet ing to an ester or nimle group chosen so that the average of all numbers a in the total ltlm of the above defined organosilicon compounds presllixample 2 llit in the reaction mixture is greater than 1, and each R" acHt0-si CHi)i-0Hi-pHfif-ocirii CHaSlCls i5(CH3)2$lClfl -l 3(CHJ)( uH5)SlCh GCHQCOQH 251,0

WIN 0 troic-cHi-c Hr-si(cHi)t+-o-siicu1n tcHt)ti-o siic uni-1 J substituent respectively is a silicon bonded hydrocarbon radical selected from the group consisting of methyl,

phenyl, and vinyl, at least half of the number of said hydrocarbon radicals contained in the reaction mixture being methyl, at boiling temperature, in general at from 80 to 100 C., until hydrolysis and co-condensation take place.

Accordingly, the various reaction stages, including the hydrolysis of the ester groups on the carbon atoms and on the silicon atoms and of the nitrile group or groups present, the decarboxylation, the hydrolysis of the chlorosilanes which may be employed, and the co-condensation of the siloxanes which may be employed, all proceed side by side during a single operation.

In accordance with a specific embodiment of the .present invention, t3-(dimethyl-ethoxy-silyl)-a-cyanopropionic acid ethyl ester is used with an organochlorosilane in the presence of acetic acid as reaction medium in a sufiicient amount of water to produce hydrochloric acid upon hydrolysis of all Cl-Si bonds present.

In accordance with another specific embodiment of the present invention, the reaction is carried out with B-(dimethyl-ethoXy-silyl)-ot-cyanopropionic acid ethyl ester and an organosiloxane free from Cl-Si groups in a mixture of glacial acetic acid and concentrated hydrochloric acid as reaction medium.

In accordance with a prefered feature of the invention, as used herein, both in the specification and claims, R defines substituents which are all methyl, or all ethyl, or both methyl and ethyl; R" defines substituents which are all methyl, or both methyl and phenyl, or both methyl and vinyl; and one, two, or three of the R substituents define fl-carboxyethyl radicals linked to separate silicon atoms while the remaining R substituents define substituents which are all methyl, both methyl and phenyl, or both methyl and vinyl.

It will be appreciated that the instant specification and examples are set forth by way of illustration, and not limitation, and that various modifications and changes may be made without departing from the spirit and scope of the present invention which is to be limited only by the scope of the appended claims.

What is claimed is:

1. Process for the production of organopolysiloxane of the general empirical formula in which n is a number having a value greater than 1 and at most equal to 3, at least one individual R substituent is fi-carboxyethyl linked to silicon and each of the remaining R substituents respectively is a hydrocarbon radical selected from the group consisting of methyl, phenyl, and vinyl, which comprises heating a ,B-organosrlyla-cyanopropionic ester of the formula (CH3)ms (OR')3-mCHQ (%H ?-OR in which m is an integer having a value from 1 to 2, and each of the R substituents is an alkyl radical having 1 to 2 carbon atoms, in a strongly acidic aqueous medium in admixture with at least one organosilicon compound selected from the group consisting of organichlorosilanes of the formula R",,SiCl and organisiloxanes of the empirical formula R.SiO

in which a is a number having a value of at most 3 yet is chosen so that the average of all numbers a in the total sum of the above defined organosilicon compounds present in the reaction mixture is greater than 1, and each R" substituent respectively is a silicon bonded hydrocarbon radical selected from the group consisting of methyl,

phenyl, and vinyl, at least half of the number of said hydrocarbon radicals contained in the reaction mixture being methyl, at boiling temperature until hydrolysis decarboxylation, and co-condensation take place, and recovering the corresponding fi-carboxyethyl-substituted organopolysiloxane thereby formed.

2. Process according to claim 1 wherein the B-organosilyl-a-cyano-propionic acid ester used is 'fi-(dimethylethoxy-silyl)--cyano-propionic acid ethyl ester.

3. Process according to claim 1 wherein the fi-organosilyl-a-cyano-propionic acid ester used is fl-(dimethyl-methoxy-silyl)-a-cyano-propionic acid ethyl ester.

4. Process according'to claim 1 wherein the reaction is carried out with an organochlorosilane, and acetic acid is used as reaction medium.

5. Process according to claim 1 wherein the reaction is carried out with an organosiloxane free from Cl-Si groups, and a mixture of glacial acetic acid and hydrochloric acid having 20m 38 percent by weight HCl is used as reaction medium.

6. Process for the production of organopolysiloxane of the general empirical formula Rnsio in which n is a number having a value greater than 1 and at most equal to 3, at least one individual R substituent is ,B-carboxyethyl linked to silicon and all the remaining R substituents together include methyl and phenyl radicals, the number of phenyl radicals being at most equal to that of the methyl radicals, which comprises heating a ,B-organosilyl-a-cyanpropionic acid ester of the formula in which m is an integer having a value from 1 to 2, and the R substituents include at least one of methyl and ethyl, in a strongly acidic aqueous medium in admixture with at least one organosilicon compound selected from the group consisting of organochlorosilanes of the formula and organosiloxanes of the empirical formula II R S10 in which a is a number having a value of at most 3 yet is chosen to that the average of all numbers "(Lin the total sum of the above defined organosilicon compounds present in the reaction mixture is greater than 1, and the R" substituents together ir'iolude methyl and phenyl radicals, the proportions being chosen so that the number of phenyl radicals contained in the total reaction mixture is at most equal to that of the silicon bonded methyl radicals therein, at boiling temperature'until hydrolysis, 'decarboxylation, and co-condensation take place and recovering the corresponding fl-carboxyethyl-substituted organopolysiloxane thereby formed.

7. Process for the production of organopolysiloxane of the general empirical formula RnSiO in which n is a number having a value greater than 1 and at most equal to 3, at least one individual R substituent is fl-carboxyethyl linked to silicon and all the remaining R substituents together include methyl and vinyl radicals, the number of vinyl radicals being at most equal to that of the methyl radicals, which comprises heating a fl-organosilyl-a-cyanoprionic acid ester of the formula (CHa)mSi(OR)a-mCH:CHCOR' in which m is an integer having a value from 1 to 2, and the R substituents include at least one of methyl and W ethyl, in a strongly acidic aqueous medium in admixture with at least one organosilicon compound selected from the group consisting of organochlorosilanes or the formula and organosi'loxanes of the empirical formula iEi".SiO

ha: It

in which a is a number having a value of at most 3 yet is chonse so that the average of all number a m the total sum of the above defined organosilicon compounds present in the reaction mixture is greater than 1 and the R substituents together include methyl and vinyl radicals, the proportions being chosen so that the number of vinyl radicals contained in the total reaction mixture is at most equal to that of the silicon bonded methyl radicals therein, at boiling temperature until hydrolysis, decorboxylation, and co-condensation take place and recovering the corresponding B-carboxyethyl-substituted organopolysilox- 430 ane thereby formed.

l Process according to claim 8, wherein 4 moles of said cyanopropionic acid ester and 5 moles of said cyclolietrasiloxane are used.

References Cited UNITED STATES PATENTS 135,168,543 Ill/1965 Black et al. 260448.2 3,182,076 5/ 1965 Holdstock 260-4482 13,208,973 W 1965 Bluestein 260448.2 XR

lOBIAS E. LEVOW, Primary Examiner.

W F. SHAVER, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Hans Niederprum et a1.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below: Column 1, line 69, "this" should read the Column 3, line 45, before "dimethyl" insert an opening parenthesis. Columns 3 and 4, in the formula at the bottom of the page,

line 4 thereof, "-CH should read -CH same formula, line 5 thereof, "3NH C Cl" should read 3NH C1 Column 7, line 11, "chonse" should read chosen line 18, "decorboxyla-" should read decarboxyla- Signed and sealed this 30th day of December 1969.

(SEAL) Attest:

Edward M. Fletcher, Jr. Attesting Officer WILLIAM E. SCHUYLER, JR.

Commissioner of Patents 

1. PROCESS FOR THE PRODUCTION OF ORGANOPOLYSILOXANE OF THE GENERAL EMPIRICAL FORMULA 